On the WebInsightLab.com blog there's a new post with a long list (30 to be exact) of PHP-based content management systems besides WordPress that you could select from for your next project.

Yes, there are many CMS available for your website, most of them are Open Source. You can not only use them but may modify too according to your need but under GNU license. [...] Now move on to other PHP Based Open Source CMS, following list shows you 30 Open Source CMS besides WordPress which can be useful to build your website and manage your content.